Acute septic arthritis is a rare, but potentially devastating disease. The treatment is initiated intravenously, but can be safely switched to oral after 2–4 days providing large doses of a well-absorbing antibiotic and, for time-dependent antibiotics, 4 times-a-day administration are used. Empiric treatment should always cover Staphylococcus aureus and common respiratory pathogens, whereas Kingella kingae and Salmonella are important only regionally. Studies conducted by our group have shown that a total course of 10 days may suffice for previously healthy children in a Western setting. Treatment of neonates, patients with immunodeficiency or cases caused by methicillin-resistant S. aureus, may deserve a different approach.